\documentclass{standalone}
\usepackage{enumitem}
\usepackage{tikz} % Required for drawings
\usetikzlibrary{shapes}
\usetikzlibrary{arrows}
\usetikzlibrary{calc}

\definecolor{mygreen}{rgb}{0,0.6,0}

\begin{document}
	\tikzstyle{state}=[draw,shape=circle]
	\tikzstyle{gstate}=[draw,shape=circle,mygreen]
	\tikzstyle{edge}=[draw,latex'-]
	\tikzstyle{gedge}=[draw,latex'-,mygreen]
	\centering
	\begin{tikzpicture}
		\draw[opacity=0.0,very thick] (0.5,4) rectangle (3.5,-1);
			
		\node at (1,4.5){$\mathcal{S}_0$};	
		\node at (2,4.5){$\mathcal{S}_1$};
		\node at (3,4.5){$\mathcal{S}_2$};
		
		\node[gstate] (s00) at (1,0) {};
		\node[gstate,dashed] (s02) at (1,2) {};
		
		\node[gstate,dashed] (s10) at (2,-0.5) {};
		\node[gstate] (s11) at (2,0.5) {};
		\node[gstate,dashed] (s12) at (2,1.5) {};
		\node[gstate,dashed] (s13) at (2,2.5) {};
		\node[gstate,dashed] (s14) at (2,3.5) {};
		
		\draw[gedge,dashed] (s00) -- (s10);
		\draw[gedge,ultra thick] (s00) -- (s11);
		\draw[gedge,dashed] (s00) -- (s12);
		\draw[gedge,dashed] (s02) -- (s13);
		\draw[gedge,dashed] (s02) -- (s14);
		
		\node[gstate,ultra thick] (s20) at (3,0) {};
		\node[gstate] (s21) at (3,1) {};
		\node[gstate] (s22) at (3,2) {};
		
		\draw[gedge] (s11) -- (s20);		
		\draw[gedge,ultra thick] (s11) -- (s21);		
		\draw[gedge] (s11) -- (s22);
	
		\draw[mygreen,very thick] (2.5,4) rectangle (3.5,-1);
	\end{tikzpicture}
\end{document}
